What is an ICD9 Code?

An ICD9 code is a numeric diagnostic code used by insurance companies to determine whether or not to pay for a medical test, treatment, or procedure. ICD stands for International Classification of Diseases, and the 9th edition is the most recent publication, with ICD10 scheduled for publication in 2013. ICD9 codes are used together with CPT, or Current Procedural Terminology codes, in the medical billing process. CPT codes are used to describe the test or procedure itself, while ICD9 codes describe the patient's medical condition that warranted the treatment. Without the medical justification provided by the ICD9 diagnostic code, many insurance companies will not pay the associated claim.

Anytime you are treated by a doctor or hospital, a bill will be sent to your insurance company. The doctor's office uses a system called coding to tell the insurance company why you were treated, and what treatments the doctor is asking payment for. CPT codes are used to describe the treatments you actually received, such as a physical examination or an x-ray. The ICD9 code is a diagnostic code that tells why you received the treatment; it may describe your symptoms, or it may describe known medical conditions such as hypertension or diabetes. Insurance companies then decide if the treatment you received was medically necessary, or appropriate, for the diagnoses listed.

You may wonder why medical providers and insurance companies use numerical coding for the billing process, instead of just listing the name of the procedure or the diagnosis. The biggest advantage of using numeric coding is that it provides a uniform system that is accepted by nearly all doctors and insurance companies, which helps eliminate confusion. Medical terminology is often based on Latin and scientific terms, which can be easily misspelled or used in the wrong context, and can be very cumbersome to write or type into the billing system. The numeric coding system streamlines the billing process for both the medical staff and the insurance company.

The coding system also allows computer software to efficiently compare CPT codes with ICD9 codes and look for a logical relationship. For example, a bill for a chest x-ray makes logical sense if the bill has an ICD9 code listing "shortness of breath" as a symptom. This bill would likely be paid without unnecessary delays. However, a bill for a foot x-ray, if accompanied by an ICD9 code describing a finger injury, would be rejected by the computer software as an error. This bill would then be sent back to the medical staff for correction before it can be paid.

Because medical technologies change so rapidly, it is important to have the most up-to-date copies of both the ICD9 manual and the CPT manual. Both sets of codes are revised every year, and revisions are available in both print and electronic versions. CPT codes are published by the American Medical Association. ICD9 codes are maintained by National Center for Health Statistics (NCHS) and Centers for Medicare and Medicaid Services (CMS). You can order updated manuals directly from either of these organizations, but you can usually obtain updates from your billing software vendor as well.